Zinc base alloys



Patented Jan. 8, 1946 ZINC BASE ALLOYS Edward S. Bunn, Rome, N. Y., assignor to Revere Copper and Brass Incorporated. Rome, N. Y., a corporation of Maryland No Drawing.

2 Claims.

My invention, which relates to zinc base alloys, and has among its objects the provision-of a zinc base alloy of improved characteristics, ,will be best understood from the following description, the scope of the invention being more particularly pointed out in the appended claims.

Within the limitations hereinafter set forth, the alloys according to the invention contain 0.3 to 0.9% copper and 0.2 to 0.6% silicon.

Zinc, itwill be understood by those skilled in inch, and a low degree of toughness represented by a Charpy impact strength of about 48 foot pounds per square inch. When such hot rolled zinc is subjected to moist steam at 95C. for days, which is the standard accepted test for determining the effect of age on the properties of zinc and its alloys, the original excellent ductility of the metal almost disappears, being then Application September 1, 1943, Serial No. 500,840

represented by an elongation of only about 2% in 2 inches, while its original tensile strength of 17,000 pounds per square inch is reduced to the low value of 11,000 pounds per square inch and its toughness to the low value represented by sile strength of zinc as it ages it has been found occurs because it undergoes with age a coarsening of its crystalline structure, this phenomena commonly called grain growt Applicant has found that if copper and silicon are added to zinc in proper proportions within the ranges above specified its toughness and tensile strength can be increased without in any instance seriously 66 amount of silicon,

diminishing its ductility and in fact in many instances improving the latter, and that these propcopper the percentage amount of silicon does not exceed a value which varies from 0.15 to 0.6% directly and linearly with the percentage amount of copper, that is to say, does not exceed substantially 150% of the amount of copper when the latter is 0.4% or less. If the copper and silicon are otherwise proportioned it has been found that no assurance will be had that the alloy will be satisfactorily stable in respect to ductility and toughness as it ages. For example, both, the alloy with 0.1% copper and 0.07% silicon, which is within these proportions, and the alloy with 0.1% copper and 0.6% silicon, which is outside them, have in the hot rolled condition a ductility not inferior to that of zinc, but after being subjected to the above mentioned steam test the alloy with 0.6% silicon will have a duetility corresponding to an elongation of only about 19% in 2 inches as compared to 45% for unaged zinc, while the alloy with 0.07% silicon will have a ductility" corresponding to an e1on- It has been found that appreciable increases in the tensile strength will be secured with as little as 0.1% copper. When the amount of copper exceeds about 0.9% the ductility of the alloy in the aged condition is unsatisfactorily low for many uses, and the a1loy.cold works with difliculty in a commercial sense. Within these limits of copper the Charpy impact strength, which is a measure of toughness, can be varied from about 125 to 400 foot pounds per square inch in the unaged condition and from about 100 to 400 in the aged condition by varying the amount of copper, the greater the, amount of copper the greater the impact strength. The, tensile strength can be varied in the same way from about 18,000 to 35,000 pounds per square inch in the unaged condition and from about 18,000 to 32,000 pounds per square inch in the aged condition. 'The ductility likewise may be varied by varying the amount of copper, ductilities in the unaged condition of the hot worked alloy correspondingto 40 to elongation in 2 inches, and 40 to 50% in the aged condition, being secured in this way. Commonly for any given amount of copper the tensile strength and ductility can be somewhat varied by varying the particularly when the amount hot rolled, condition, by increasing the amount of silicon from 0.07 to 0.6%. range of copper any amount of silicon within the ranges and proportions thereof specified will keep the ductility at a high value and the tensile strength and toughness remarkably stable as the .alloy ages.

Best results, in respect to securing a high de-'- nee of toughness coupled with good ductility and a high tensile strength, will be had when the copper is within the range of 0.3 to 0.9% and the silicon is at least 0.2%. Within these ranges the hot rolled alloy will have a tensile strength of from 25,000 to 35,000 pounds per square inch in the unaged condition and 24,000 to 32,000 in the aged condition, coupled with corresponding elongations of 55 to' 60% and 45 to 50% in 2 inches and with Charpy impact strength of 330 to 400 and 325 to 400 foot pounds per square inch.

The attempt to eliminate or diminish grain growth in zinc by adding small amounts of other elements heretofore has commonly resulted, as the alloy ages, in causing intergranular corrosion, alloy phase changes which make articles made of the alloy unstable in respect to linear dimensions, and reduction in the cold workability of the zinc. The improved alloy, however, is substantially free from these defects, and may be readily hot and cold rolled 'into rods and sheets,

hot forged, and hot or cold extruded into various shapes, by commercial mill processes.

To secure best results in respect to freedom from intercrystalline corrosion and resistance to corrosive media it is desirable to employ in the improved alloy commercial zinc of fairly high purity as, for example, that termed High Grade No. 1 in A. S. T. M. specification 36-37, which latter grade contains a maximum of 0.07% each of lead and cadmium impurities and a maximum of 0.02% iron impurity, the total of such of these impurities as may be present not exceeding 0.1%, and is substantially free from all other impuri- Within the entire.

ties, although the iron impurity however is not particularly objectionable in any ordinary case.

with poorer commercial grades of zinc the alloy commonly will have the same mechanical characteristlcs, but may be somewhat less corrosion resistant in both respects mentionedand have more or less dimensional instability.

The excellent properties of the improved alloy 'are shown by the following table, in which the steam test is that above referred to:

' Hot tolled, and sub- Percentages As hot rolled to M to Cu Si '1 E 0 T E C 0 0 i7 45 48 ll 2 32 0. l 0.07 18 18 42 mo 0. 4 0. 07 25 55 325 24 45 320 0. 4 0. 6 28 60 330 2! 47 325 0. 9 0. 07 30 40 400 28 42 400 0. 9 0. 6 35 55 400 32 50 4(0 T-tensile strength in l 000 fitunds per square inch. E-per cent elongation in 2 ches. C=Charpy impact strength in foot pounds per square inch.

It will be understood that within the scope oi the appended claims further constituents may be added for modifying the properties of the improved alloy or for securing additional properties so long as the characteristics imparted to the zinc by the addition 0'! copper and silicon are not substantially destroyed.

I claim:

1. Hot and cold workable zinc base alloys, characterized by a toughness and tensile strength materially greater 'anda ductility not materially inferior to those of zinc and by substantial freedom from intercrystalline corrosion, containing 0.3 to 0.9% copper and 0.2 to 0.6% silicon, the amount of silicon not exceeding substantially of the amount of copper when the latter is 0.4% or less, the balance being zinc of not less than 99.9% purity.

2. The alloys according to claim 1 of such purity that they contain not more than 0.07% each of lead and cadmium impurities and not more than 0.02% iron impurity, the total of such of 

